All known natural calcitonin peptides contain an amino acid sequence of 32 amino acids. Salmon calcitonin, for example, has the following formula: ##STR1##
In U.S. Pat. Nos. 3,926,938, 4,062,815, 3,929,758, 4,033,940 and 4,217,268 are disclosed improved syntheses of calcitonins including the salmon calcitonin referred to above.
The natural calcitonins include the salmon, eel, bovine, porcine, ovine, rat and human calcitonins. All of these have either valine or methonine at position number 8 and either phenylalanine or tyrosine at position number 22.